Re: [PATCH 2/6] vhost: get guest/host physical address mappings

On Tue, Aug 23, 2016 at 11:58:42AM +0200, Maxime Coquelin wrote:

quoted

+/* Convert guest physical address to host physical address */
+static inline phys_addr_t __attribute__((always_inline))
+gpa_to_hpa(struct virtio_net *dev, uint64_t gpa, uint64_t size)
+{
+	uint32_t i;
+	struct guest_page *page;
+
+	for (i = 0; i < dev->nr_guest_pages; i++) {
+		page = &dev->guest_pages[i];
+
+		if (gpa >= page->guest_phys_addr &&
+		    gpa + size < page->guest_phys_addr + page->size) {

Shouldn't be '<=' here?

Oops, you are right.

quoted

+			return gpa - page->guest_phys_addr +
+			       page->host_phys_addr;
+		}
+	}
+
+	return 0;
+}
+
struct virtio_net_device_ops const *notify_ops;
struct virtio_net *get_device(int vid);

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index d2071fd..045d4f0 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c

@@ -372,6 +372,81 @@ vhost_user_set_vring_base(struct virtio_net *dev,

	return 0;
}

+static void
+add_one_guest_page(struct virtio_net *dev, uint64_t guest_phys_addr,
+		   uint64_t host_phys_addr, uint64_t size)
+{
+	struct guest_page *page;
+
+	if (dev->nr_guest_pages == dev->max_guest_pages) {
+		dev->max_guest_pages *= 2;
+		dev->guest_pages = realloc(dev->guest_pages,
+					dev->max_guest_pages * sizeof(*page));

Maybe realloc return could be checked?

Yes, I should have done that. Besides, I also forgot to free it at
somewhere. Will fix it.

quoted

+	}
+
+	page = &dev->guest_pages[dev->nr_guest_pages++];
+	page->guest_phys_addr = guest_phys_addr;
+	page->host_phys_addr  = host_phys_addr;
+	page->size = size;
+}
+
+static void
+add_guest_pages(struct virtio_net *dev, struct virtio_memory_region *reg,
+		uint64_t page_size)
+{
+	uint64_t reg_size = reg->size;
+	uint64_t host_user_addr  = reg->host_user_addr;
+	uint64_t guest_phys_addr = reg->guest_phys_addr;
+	uint64_t host_phys_addr;
+	uint64_t size;
+	uint32_t pre_read;
+
+	pre_read = *((uint32_t *)(uintptr_t)host_user_addr);
+	host_phys_addr = rte_mem_virt2phy((void *)(uintptr_t)host_user_addr);
+	size = page_size - (guest_phys_addr & (page_size - 1));
+	size = RTE_MIN(size, reg_size);
+
+	add_one_guest_page(dev, guest_phys_addr, host_phys_addr, size);
+	host_user_addr  += size;
+	guest_phys_addr += size;
+	reg_size -= size;
+
+	while (reg_size > 0) {
+		pre_read += *((uint32_t *)(uintptr_t)host_user_addr);
+		host_phys_addr = rte_mem_virt2phy((void *)(uintptr_t)host_user_addr);
+		add_one_guest_page(dev, guest_phys_addr, host_phys_addr, page_size);
+
+		host_user_addr  += page_size;
+		guest_phys_addr += page_size;
+		reg_size -= page_size;
+	}
+
+	/* FIXME */
+	RTE_LOG(INFO, VHOST_CONFIG, ":: %u ::\n", pre_read);

For my information, what is the purpose of pre_read?

Again, I put a FIXME here, but I forgot to add some explanation.

Here is the thing: the read will make sure the kernel populate the
corresponding PTE entry, so that rte_mem_virt2phy() will return proper
physical address, otherwise, invalid value is returned.

I can't simply do the read but do not actually reference/consume it.
Otherwise, the compiler will treat it as some noops and remove it.

An ugly RTE_LOG will make sure the read operation is not eliminated.
I'm seeking a more proper way to achieve that. Maybe I can add a new
field in virtio_net structure and store it there.

Or, do you have better ideas?

	--yliu